/*
 * Copyright (c) 2005, 2011, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */
/*
 * $Id: TransformService.java,v 1.6.4.1 2005/09/15 12:42:11 mullan Exp $
 */
package javax.xml.crypto.dsig;

import java.security.InvalidAlgorithmParameterException;
import java.security.NoSuchAlgorithmException;
import java.security.NoSuchProviderException;
import java.security.Provider;
import java.security.Provider.Service;
import java.security.Security;
import java.util.*;
import javax.xml.crypto.MarshalException;
import javax.xml.crypto.XMLStructure;
import javax.xml.crypto.XMLCryptoContext;
import javax.xml.crypto.dsig.spec.TransformParameterSpec;

import sun.security.jca.*;
import sun.security.jca.GetInstance.Instance;

/**
 * A Service Provider Interface for transform and canonicalization algorithms.
 *
 * <p>Each instance of <code>TransformService</code> supports a specific transform or
 * canonicalization algorithm and XML mechanism type. To create a <code>TransformService</code>,
 * call one of the static {@link #getInstance getInstance} methods, passing in the algorithm URI and
 * XML mechanism type desired, for example:
 *
 * <blockquote><code> TransformService ts = TransformService.getInstance(Transform.XPATH2, "DOM");
 * </code></blockquote>
 *
 * <p><code>TransformService</code> implementations are registered and loaded using the {@link
 * java.security.Provider} mechanism.  Each <code>TransformService</code> service provider
 * implementation should include a <code>MechanismType</code> service attribute that identifies the
 * XML mechanism type that it supports. If the attribute is not specified, "DOM" is assumed. For
 * example, a service provider that supports the XPath Filter 2 Transform and DOM mechanism would be
 * specified in the <code>Provider</code> subclass as:
 * <pre>
 *     put("TransformService." + Transform.XPATH2,
 *         "org.example.XPath2TransformService");
 *     put("TransformService." + Transform.XPATH2 + " MechanismType", "DOM");
 * </pre>
 * <code>TransformService</code> implementations that support the DOM mechanism type must abide by
 * the DOM interoperability requirements defined in the <a href="../../../../../technotes/guides/security/xmldsig/overview.html#DOM
 * Mechanism Requirements"> DOM Mechanism Requirements</a> section of the API overview. See the <a
 * href="../../../../../technotes/guides/security/xmldsig/overview.html#Service Provider"> Service
 * Providers</a> section of the API overview for a list of standard mechanism types. <p> Once a
 * <code>TransformService</code> has been created, it can be used to process <code>Transform</code>
 * or <code>CanonicalizationMethod</code> objects. If the <code>Transform</code> or
 * <code>CanonicalizationMethod</code> exists in XML form (for example, when validating an existing
 * <code>XMLSignature</code>), the {@link #init(XMLStructure, XMLCryptoContext)} method must be
 * first called to initialize the transform and provide document context (even if there are no
 * parameters). Alternatively, if the <code>Transform</code> or <code>CanonicalizationMethod</code>
 * is being created from scratch, the {@link #init(TransformParameterSpec)} method is called to
 * initialize the transform with parameters and the {@link #marshalParams marshalParams} method is
 * called to marshal the parameters to XML and provide the transform with document context. Finally,
 * the {@link #transform transform} method is called to perform the transformation. <p>
 * <b>Concurrent Access</b> <p>The static methods of this class are guaranteed to be thread-safe.
 * Multiple threads may concurrently invoke the static methods defined in this class with no ill
 * effects.
 *
 * <p>However, this is not true for the non-static methods defined by this class. Unless otherwise
 * documented by a specific provider, threads that need to access a single
 * <code>TransformService</code> instance concurrently should synchronize amongst themselves and
 * provide the necessary locking. Multiple threads each manipulating a different
 * <code>TransformService</code> instance need not synchronize.
 *
 * @author Sean Mullan
 * @author JSR 105 Expert Group
 * @since 1.6
 */
public abstract class TransformService implements Transform {

  private String algorithm;
  private String mechanism;
  private Provider provider;

  /**
   * Default constructor, for invocation by subclasses.
   */
  protected TransformService() {
  }

  /**
   * Returns a <code>TransformService</code> that supports the specified
   * algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type
   * (ex: DOM).
   *
   * <p>This method uses the standard JCA provider lookup mechanism to
   * locate and instantiate a <code>TransformService</code> implementation
   * of the desired algorithm and <code>MechanismType</code> service
   * attribute. It traverses the list of registered security
   * <code>Provider</code>s, starting with the most preferred
   * <code>Provider</code>. A new <code>TransformService</code> object
   * from the first <code>Provider</code> that supports the specified
   * algorithm and mechanism type is returned.
   *
   * <p> Note that the list of registered providers may be retrieved via
   * the {@link Security#getProviders() Security.getProviders()} method.
   *
   * @param algorithm the URI of the algorithm
   * @param mechanismType the type of the XML processing mechanism and representation
   * @return a new <code>TransformService</code>
   * @throws NullPointerException if <code>algorithm</code> or <code>mechanismType</code> is
   * <code>null</code>
   * @throws NoSuchAlgorithmException if no <code>Provider</code> supports a
   * <code>TransformService</code> implementation for the specified algorithm and mechanism type
   * @see Provider
   */
  public static TransformService getInstance
  (String algorithm, String mechanismType)
      throws NoSuchAlgorithmException {
    if (mechanismType == null || algorithm == null) {
      throw new NullPointerException();
    }
    boolean dom = false;
    if (mechanismType.equals("DOM")) {
      dom = true;
    }
    List<Service> services = GetInstance.getServices("TransformService", algorithm);
    for (Iterator<Service> t = services.iterator(); t.hasNext(); ) {
      Service s = t.next();
      String value = s.getAttribute("MechanismType");
      if ((value == null && dom) ||
          (value != null && value.equals(mechanismType))) {
        Instance instance = GetInstance.getInstance(s, null);
        TransformService ts = (TransformService) instance.impl;
        ts.algorithm = algorithm;
        ts.mechanism = mechanismType;
        ts.provider = instance.provider;
        return ts;
      }
    }
    throw new NoSuchAlgorithmException
        (algorithm + " algorithm and " + mechanismType
            + " mechanism not available");
  }

  /**
   * Returns a <code>TransformService</code> that supports the specified
   * algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type
   * (ex: DOM) as supplied by the specified provider. Note that the specified
   * <code>Provider</code> object does not have to be registered in the
   * provider list.
   *
   * @param algorithm the URI of the algorithm
   * @param mechanismType the type of the XML processing mechanism and representation
   * @param provider the <code>Provider</code> object
   * @return a new <code>TransformService</code>
   * @throws NullPointerException if <code>provider</code>, <code>algorithm</code>, or
   * <code>mechanismType</code> is <code>null</code>
   * @throws NoSuchAlgorithmException if a <code>TransformService</code> implementation for the
   * specified algorithm and mechanism type is not available from the specified
   * <code>Provider</code> object
   * @see Provider
   */
  public static TransformService getInstance
  (String algorithm, String mechanismType, Provider provider)
      throws NoSuchAlgorithmException {
    if (mechanismType == null || algorithm == null || provider == null) {
      throw new NullPointerException();
    }

    boolean dom = false;
    if (mechanismType.equals("DOM")) {
      dom = true;
    }
    Service s = GetInstance.getService
        ("TransformService", algorithm, provider);
    String value = s.getAttribute("MechanismType");
    if ((value == null && dom) ||
        (value != null && value.equals(mechanismType))) {
      Instance instance = GetInstance.getInstance(s, null);
      TransformService ts = (TransformService) instance.impl;
      ts.algorithm = algorithm;
      ts.mechanism = mechanismType;
      ts.provider = instance.provider;
      return ts;
    }
    throw new NoSuchAlgorithmException
        (algorithm + " algorithm and " + mechanismType
            + " mechanism not available");
  }

  /**
   * Returns a <code>TransformService</code> that supports the specified
   * algorithm URI (ex: {@link Transform#XPATH2}) and mechanism type
   * (ex: DOM) as supplied by the specified provider. The specified provider
   * must be registered in the security provider list.
   *
   * <p>Note that the list of registered providers may be retrieved via
   * the {@link Security#getProviders() Security.getProviders()} method.
   *
   * @param algorithm the URI of the algorithm
   * @param mechanismType the type of the XML processing mechanism and representation
   * @param provider the string name of the provider
   * @return a new <code>TransformService</code>
   * @throws NoSuchProviderException if the specified provider is not registered in the security
   * provider list
   * @throws NullPointerException if <code>provider</code>, <code>mechanismType</code>, or
   * <code>algorithm</code> is <code>null</code>
   * @throws NoSuchAlgorithmException if a <code>TransformService</code> implementation for the
   * specified algorithm and mechanism type is not available from the specified provider
   * @see Provider
   */
  public static TransformService getInstance
  (String algorithm, String mechanismType, String provider)
      throws NoSuchAlgorithmException, NoSuchProviderException {
    if (mechanismType == null || algorithm == null || provider == null) {
      throw new NullPointerException();
    } else if (provider.length() == 0) {
      throw new NoSuchProviderException();
    }
    boolean dom = false;
    if (mechanismType.equals("DOM")) {
      dom = true;
    }
    Service s = GetInstance.getService
        ("TransformService", algorithm, provider);
    String value = s.getAttribute("MechanismType");
    if ((value == null && dom) ||
        (value != null && value.equals(mechanismType))) {
      Instance instance = GetInstance.getInstance(s, null);
      TransformService ts = (TransformService) instance.impl;
      ts.algorithm = algorithm;
      ts.mechanism = mechanismType;
      ts.provider = instance.provider;
      return ts;
    }
    throw new NoSuchAlgorithmException
        (algorithm + " algorithm and " + mechanismType
            + " mechanism not available");
  }

  private static class MechanismMapEntry implements Map.Entry<String, String> {

    private final String mechanism;
    private final String algorithm;
    private final String key;

    MechanismMapEntry(String algorithm, String mechanism) {
      this.algorithm = algorithm;
      this.mechanism = mechanism;
      this.key = "TransformService." + algorithm + " MechanismType";
    }

    public boolean equals(Object o) {
      if (!(o instanceof Map.Entry)) {
        return false;
      }
      Map.Entry<?, ?> e = (Map.Entry<?, ?>) o;
      return (getKey() == null ?
          e.getKey() == null : getKey().equals(e.getKey())) &&
          (getValue() == null ?
              e.getValue() == null : getValue().equals(e.getValue()));
    }

    public String getKey() {
      return key;
    }

    public String getValue() {
      return mechanism;
    }

    public String setValue(String value) {
      throw new UnsupportedOperationException();
    }

    public int hashCode() {
      return (getKey() == null ? 0 : getKey().hashCode()) ^
          (getValue() == null ? 0 : getValue().hashCode());
    }
  }

  /**
   * Returns the mechanism type supported by this <code>TransformService</code>.
   *
   * @return the mechanism type
   */
  public final String getMechanismType() {
    return mechanism;
  }

  /**
   * Returns the URI of the algorithm supported by this
   * <code>TransformService</code>.
   *
   * @return the algorithm URI
   */
  public final String getAlgorithm() {
    return algorithm;
  }

  /**
   * Returns the provider of this <code>TransformService</code>.
   *
   * @return the provider
   */
  public final Provider getProvider() {
    return provider;
  }

  /**
   * Initializes this <code>TransformService</code> with the specified
   * parameters.
   *
   * <p>If the parameters exist in XML form, the
   * {@link #init(XMLStructure, XMLCryptoContext)} method should be used to
   * initialize the <code>TransformService</code>.
   *
   * @param params the algorithm parameters (may be <code>null</code> if not required or optional)
   * @throws InvalidAlgorithmParameterException if the specified parameters are invalid for this
   * algorithm
   */
  public abstract void init(TransformParameterSpec params)
      throws InvalidAlgorithmParameterException;

  /**
   * Marshals the algorithm-specific parameters. If there are no parameters
   * to be marshalled, this method returns without throwing an exception.
   *
   * @param parent a mechanism-specific structure containing the parent node that the marshalled
   * parameters should be appended to
   * @param context the <code>XMLCryptoContext</code> containing additional context (may be
   * <code>null</code> if not applicable)
   * @throws ClassCastException if the type of <code>parent</code> or <code>context</code> is not
   * compatible with this <code>TransformService</code>
   * @throws NullPointerException if <code>parent</code> is <code>null</code>
   * @throws MarshalException if the parameters cannot be marshalled
   */
  public abstract void marshalParams
  (XMLStructure parent, XMLCryptoContext context)
      throws MarshalException;

  /**
   * Initializes this <code>TransformService</code> with the specified
   * parameters and document context.
   *
   * @param parent a mechanism-specific structure containing the parent structure
   * @param context the <code>XMLCryptoContext</code> containing additional context (may be
   * <code>null</code> if not applicable)
   * @throws ClassCastException if the type of <code>parent</code> or <code>context</code> is not
   * compatible with this <code>TransformService</code>
   * @throws NullPointerException if <code>parent</code> is <code>null</code>
   * @throws InvalidAlgorithmParameterException if the specified parameters are invalid for this
   * algorithm
   */
  public abstract void init(XMLStructure parent, XMLCryptoContext context)
      throws InvalidAlgorithmParameterException;
}
